Rendering to AVCHD with Progressive Scanning

Hi,

I'm using Sony Vegas 11 Pro.

I have a Panasonic HDC-SD9EB-S HD Camcorder which I use to record my movies in Full HD 1920 x 1080 25p (PAL) in AVCHD format (*.m2ts). I can setup a custom project template fine (no existing template seems to match) but I'm struggling to select the best setting for rendering.

I want to render to a format as close to my source as possible. When I try to render to AVCHD I am unable to select 'Progressive Scanning' and I'm forced to accept 'Interlacing' (Field Order: Upper Field First is set and option grayed out so can't set to 'None'!). To get progressive scanning with audio included I'm having to use *.mp4. As my source is in 1080p (progressive) I don't want to have to render to 1080i (interlaced), as it will lower quality and cause those dodgy lines when panning.

Alternatively I eventually want to author to Blu-ray so is there a better render option to avoid re-encoding when authoring to Blu-ray?